BENDABLE TIP ASSEMBLIES FOR CATHETERS

Abstract: A bendable tip assembly (16) attachable to the end of a catheter (14) includes a movable internal stiffening member (61) for changing the bending characteristics of the assembly (16).

Description: BENDABLE TIP ASSEMBLIES FOR CATHETERS Field of the Invention This invention relates to bendable tip as¬ semblies for catheters. Background of the Invention Cardiac mapping is used to locate aberrant electrical pathways and currer ts emanating within the heart. Such aberrant pathways cause irregular contractions of the heart muscle resulting in life- threatening patterns or disrhythmias. Intercardiac mapping requires careful posi¬ tioning of the electrodes within the heart. Various steering mechanisms for catheters carrying such electrodes have heretofore been developed and used. To provide catheters having different curve configurations to access various endocardial sites, physicians have to stock and use number of differ¬ ent catheters, each of which provides a different curve configuration. Commercially available cathe- ters, thus, come in sets, which often provide 4 to 7 different curve configurations by using different catheters. This approach presents serious disadvan¬ tages, because the physician often must repeatedly remove and re-inserc these different catheters to complete a procedure on a given patient. Summary of the Invention The present invention provides a catheter, usable in both diagnostic and therapeutic applica- tions, that enables a physician to swiftly and accu¬ rately change the configuration or steering charac¬ teristics of the distal curve of the catheter as it is steered within the body of a patient. The cathe¬ ter that embodies the invention allows physicians to access many more endocardium sites than heretofore achievable by a single catheter. In its broadest aspect, the invention provides a catheter which en¬ ables a physician to alter the physical characteris¬ tics of a catheter inserted within a living body by manipulation of external controls. One aspect of the invention provides a catheter having an internal fulcrum that can be moved within the catheter to different distances relative to the distal tip by external manipulation. Movement of the internal fulcrum results in creating different curvature radii for bending of the distal tip. The internal fulcrum that this aspect of the invention provides is usable in connection with unidirectional catheters, as well as bi-directional, steerable catheters. This aspect of the invention provides a catheter in which a longer fulcrum-to-distal tip distance can be provided for accessing and measuring electrical activity in portions of the heart such as the coronary sinus, the right ventricular overflow tract and the HIS bundle. Similarly, a shorter fulcrum-to-tip distance can be used to access such areas as the high right atrium and the right and left ventricle apex of the heart. Another aspect of the invention provides a catheter having an internal stiffening meml-er that can be moved within the catheter to either a dis- tally extended or retracted location within the dis- tal tip by external manipulation. Movement of the internal stiffening member results in creating dif¬ ferent ease of steering characteristics for bending of the distal tip. The internal stiffening member that the invention provides is usable in connection with unidirectional catheters, as well as bi-direc¬ tional, steerable catheters. This aspect of the invention provides a catheter in which a stiffening member is distally extended within the tip distance to provide greater rigidity and thusr-stiffer steering characteristics and retracted.to a more proximal position to provide the tip with less stiffness and hence easier steer¬ ing characteristics requiring less steering force. Thus the ease of accessing and measuring electrical activity in all portions of the heart is increased. Further, objects and advantages of the in¬ vention will become apparent from the following de¬ tailed description and accompanying drawings. Brief Description of Drawings Figure l is a top view of a catheter and catheter handle assembly in accordance with the in¬ vention with some interior parts shown by means of phantom lines; Figure 2 is a view of the catheter shown in Figure 1 with the tip portion broken away and shown in cross-section on a greatly enlarged scale and showing a moveable sleeve in a proximal position; Figure 3 is a view in accordance with Fig¬ ure 2 showing the sleeve in a more distal position; Figure 4 is a top sectional view of the handle of the device of the present invention on a greatly enlarged scale; Figure 5 is a sectional view of a tip por¬ tion of a catheter in accordance with another e - bodi ent of the invention; Figure 6 is a view of the device of Figure 5 with the curve adjusting mandrel advanced to a more distal position; Figure 7 is a view of a catheter showing an alternate embodiment of the invention utilizing a rotatable sleeve; Figure 8 is a perspective view showing the configuration of the distal end of the sleeve of the device shown in Figure 7; Figure 9 is a fragmentary cross-sectional view showing the control mechanism in the distal portion of the handle of the handle of the catheter of Figure 7; Figure 10 is a view of a catheter showing bendable axially movable stiffening member in a re¬ tracted approximal position, and; Figure 11 is a sectional view of the distal tip portion of the catheter of Figure 10 with the stiffening member advanced to its most distal posi- tion. Detailed Description of Preferred Embodiments Figure 1 shows a steerable catheter 10 that embodies the features of the invention. The cathe¬ ter 10 includes several main parts: a handle 12, a catheter tube or body 14, and a steerable distal tip assembly 16. In use, the catheter 10 provides elec- trophysiology diagnosis or therapy in the interior regions of the heart. When used for this purpose, a physician grips the handle 12 and maneuvers the catheter body 14 through a main vein or artery (which is typically the femoral vein) into the interior region of the heart that is to be treated. The physician then further steers the distal tip assembly 16 to place it in contact with the tissue that is to be ablated. The physician directs energy to an electrode in the assembly 16 to ablate the tissue contacted. As Figure 4 shows, the handle 12 encloses a steering mechanism which may be in the form of a rotating cam wheel of the type shown in U. S. Patent 5,195,968. While one form of steering mechanism 18 is shown for purposes of illustration, it will be understood that many other mechanisms that allow for selective pulling of the steering wires in the cath- eter can be substituted. As Figure 4 best shows, the handle assembly 12 includes a housing 20 that encloses the steering mechanism 18. The steering mechanism 18 includes a rotatable wheel or cam 22 carried on a shaft 24 within the housing 20. The rotatable cam 22 and control knob 26 are attached to shaft 24 by splines. Clockwise movement of the control knob 26 rotates the cam 22 clockwise pulling on wire 56. Counter¬ clockwise movement of the control knob 26 reverses the direction of each of these movements and results in pulling wire 58. Various other mechanisms can be substituted to apply tension to wires 56 and 58 in place of that shown in Figure 4. The steering wires 56 and 58 exit the front of the housing 20 through the interior bore of a tension screw assembly 60. The distal ends of the steering wires 56 and 58 are attached to a steering wire or spring in the electrode tip assembly 16. The catheter body 14 is a flexible shaft attached to the handle 12. While it can be vari- ously constructed, in a preferred embodiment, the catheter body 14 is a length of stainless steel coiled into a flexible spring 25 enclosing an inte¬ rior bore 27 which in turn is enclosed in a braided sheath 29 of plastic material. The steering wires 56 and 58 preferably pass through the interior bore 27, which leads to the distal tip assembly 16 where the steering wire are attached to a bendable main sup¬ port wire 34. In the illustrated embodiment, the main support wire 34 is made of stainless steel flat wire stock in an elongated shape about .035 inch wide and about .005 inch thick. The main support wire 34 is about 3 inches in total length. In the distal end of the catheter body 14 there is no surrounding sheath or shield, leaving the steering assembly exposed. Positioned in the distal end region and overlying the distal end of coil 25 is a curve adjusting tube 61. The proximal end of curve adjusting tube 61 is attached to a man- drel 62 that extends within the catheter body 14 into handle 12. The proximal end of mandrel 62 is connected to a slidable, bi-directional adjuster knob 64. Sliding of knob 64 enables the practitio¬ ner to slide the adjusting tube 61 axially within the catheter body 14 to a more proximal or more dis¬ tal location as desired. The more proximal and more distal positions of knob 64 are shown in Figure 1 by means of phantom lines. In the more proximal loca¬ tion illustrated in Figure 2, the curve adjusting tube 61 is positioned to permit the maximum curva¬ ture of distal tip assembly 16 to position 16a il¬ lustrated by means of phantom lines. In the more distal location illustrated in Figure 3, the tube 61, which acts as a slidable fulcrum for the tip, steering of the tip by means of knob 26 causes a shorter portion of the tip 16 to curve to a sharper curve illustrated by phantom lines 16b in Figure 3. In the alternate embodiment illustrated in Figures 5 and 6, the mandrel 62, which may be pro- vided with an enlarged end section, is positioned for axial sliding within a channel 66 in similar to that shown in Figures 2 and 3 the distal tip 16 can be bent to different curvatures 16a or 16b as shown in Figures 5 and 6. It will readily be apparent that intermediate curve shapes other than those il¬ lustrated by lines 16a and 16b can be provided by positioning level 64 in an intermediate position. In the preferred embodiment c? the rvice shown in Figures 2 and 3 outer sleeve 29 iε .-rmed of Kevlar. Mandrel 62 is formed of a 0.02 inch stainless steel wire running parallel between the guide coil 25 and the inside of Kevlar tubing 29. Wire 64 is preferably attached on the outside of a 2.5 inch long 0.050 inch inter diameter/0.055 inch outer diameter length of tube that forms sleeve 60. The tube can be made of stainless steel, nitinol alloy or a polymeric material such as polyamide or other polymer. In the preferred embodiment, a poly¬ amide tube is reinforced by a stainless steel coil embedded in the wall. To provide a well defined movable fulcrum the sleeve is formed of a rigid ma¬ terial. It will also be apparent that in the event the tube 61 is made from a relatively softer mate¬ rial or more flexible material such as a polyurethane, silicone, or polyethylene, it will provide a stiffening effect but have less effect on the changing of the curve radius of the tip. In a further embodiment shown in Figures 7- 9 a tube 160 is rotatable relative to the steering wire 34 rather than being axially movable relative thereto. In this case a rotatable sleeve concentric with spring 25 and located within bore 27 is at¬ tached to tube 160 for the purpose of applying rota¬ tional forces thereto. Tube 160 is provided with a distal end having circumferential segments 162, 164, 166, and 168 of differing lengths. Each of these circumferential segments provides a fulcrum or stiffening member spaced a different distance from the distal tip of the catheter and thus provides for as many different curvature shapes of the tip as there are segments. Tube 160 is rotated by applying a force to control knob 170 located in handle 12. Tube 160 is connected to control handle 170 by means of a torque transmitting tube 172. Since the control wire 34 will tend to bend the distal tip 16 from side to side in a single plane, the fulcrum length provided by rotatable tube 160 is dependent on which of the segments 162, 164, 166 or 168 is positioned in the plane in which control wire 34 bends. Appropriate markings on handle 12 can be provided to indicate the position in which control knob 170 is rotated. Thus, the physician can readily change the fulcrum length or stiffness characteristics of the distal tip of the catheter by manually rotating knob 170. In the embodiment of Figure 10, a stiffen¬ ing member 180 is shown in the form of a flexible polymeric tube. Any flexible material can be used as a material of construction for tube 180. A rod 62 of the type in Figures 5 and 6 is used as a stiffening member. Any flexible materials such as plastic, metal or other bendable materials of con¬ struction can be used. Referring to Figures 10 and 11, when sleeve 180 is in the retracted position shown in Figure 10, the tip 16 can be steered easily with greatly re¬ duced resistance to bending when bending forces are applied to the tip by means of steering mechanism 18. When the stiffening member 180 is advanced to its most d. jtal position shown in Figure 11, the same catheter can behave as one that is stiffer or resistant to bending. By placing a flexib_e stiffen¬ ing member in an intermediate position, it is possi¬ ble to alter the curve characteristics of a catheter by stiffening a portion of the steerable tip portion but not the more distal portion thus providing a further range of possible curve configurations ob¬ tainable by the steerable catheter tip. It will, thus, be appreciated that in ac- cordance with the invention, the characteristics of the distal tip of a steerable catheter can be al¬ tered by means of movement of a remote control mem¬ ber. This alteration can occur when the catheter is being used within a living body. The invention, thus, makes possible the alteration of numerous characteristics of a catheter without the need for withdrawing the catheter from the body.

Claims: That Which is claimed is: 1. A tip assembly for a catheter includ¬ ing a body bendable in response to external forces, the body having opposite end portions, a stiffening member positioned in the cath¬ eter movable relative to said body in response to movement of an external control, and means located within the catheter for translating a force applied to an external control member to said stiffening member for causing the stiffening member to be moved in response to forces applied to said control member. 2. A tip assembly according to claim 1 and further including steering means at¬ tached to said body for applying a bending force to the body. 3. A tip assembly according to claim 2 wherein said stiffening member provides a fulcrum spaced a variable distance from the distal end of the body for varying the radius of curvature of the body in response to the applied bending force. 4. A tip assembly according to claim 1 or 2 wherein said stiffening member is distally extendable and proximally retractable by external manipulation of a control member for varying the stiffness of the body in response to an applied bending force. 5. A tip assembly according to claim 1 wherein the stiffening member comprises an annular solid sleeve. 6. A tip assembly according to claim 5 . wherein the stiffening member comprises a polymeric material or a metal. 7. A tip assembly according to claim 1 wherein said stiffening member is axially movable relative to said body. 8. A tip assembly according to claim 1 wherein said stiffening member is rotatably movable relative to said bendable body. 9. A tip assembly according to claim 1 and further including an electrode on said body. 10. A catheter having a body carrying a tip assembly according to any one of the foregoing claims. 11. A catheter according to claim 10 and further including a control stylet ex¬ tending through the length of the catheter body and attached to the stiffening member for moving the stiffening member in a distal/proximal direction. 12. A catheter according to claim 10 wherein the stiffening member is movable in response to motion applied to a slidable lever con¬ tained in a control handle on the proximal end of the catheter.

Inventors: BOURNE TOM, HOUSER RUSSELL A, BOURNE, TOM, HOUSER, RUSSELL, A.
Applicants: EP TECHNOLOGIES, EP TECHNOLOGIES, INC.
Application year: 1994
Main classification: A61B17
IPC codes: A61B18, A61M25, A61N1